FAMILY MUSCID^ 279 



gots from four to six days to grow, and pupation six to eiglit 

 days, so there may be many generations in a summer. Pro- 

 tection may be readily gained by community effort. Their 

 flight is sufficiently' restricted to make individual effort on 

 a farm well worth while, even if some nearby farms are neg- 

 lected. 



Fig. 224. — The common house fly: a, pupa removed from puparium; 

 b, hind end of body of larva in second stage; c, anal spiracles of larva in 

 fiist stage. All enlarged. (From Howard, Div. Ent., U. S. Dept. Ag.) 



Horn Fly {Hcematobio serrata Rob.-Desv.).— In the intro- 

 duction and rapid spread of this insect we have an excellent 

 illustration of the importance of gi\ing attention to the 

 injurious insects of other countries and of taking all possible 

 means to prevent their importation. 



The species in hand has been a common insect in Europe, 

 and with other members of the same genus recognized as a 

 troublesome insect, though apparently no careful study of its 

 life history has been made there. 



